Inorganic Disinfectants 179 



The most useful germicidal substances act destructively upon the 

 micro-organisms by forming chemical compounds with their cyto- 

 plasm. Thus, the salts of mercury unite with the protoplasm to 

 form an albuminate of mercury. Other germicidal agents dissolve or 

 coagulate the protoplasm; still others oxidize and so completely de- 

 stroy the cells. In the process of germicidal action many and varied 

 activities are at work, and, as aU are not understood, the subject is 

 a difficult one to handle in a limited amount of space. With the 

 salts, acids, and bases it appears from the researches of Kronig and 

 Paul* that ionization in solution plays an important part in the 

 destruction of micro-organisms. They found that double metallic 

 salts, in which the metal is a constituent of a complex ion in which 

 the concentration of the dissociated metal ions is consequently very 

 low, have very little germicidal power, but that simple salts, in which 

 the condition is reversed, have correspondingly higher germicidal 

 power. Dissociation, therfore, seems to have much to do with the 

 matter. 



Inorganic Disinfectants. 



Acids. — TKese agents are seldom employed, since the concentration required 



makes them objectionable. 

 Alkalis. — The same holds good with regard to these agents. 

 Salts. — In this group we find some of 3ie most powerful and most useful 

 germicidal substances. 

 Copper Sulphate. — It is curious and interesting that while this salt is highly 

 destructive to algas and other low forms of vegetable life, it is not of 

 much value for the destruction of bacteria. Its chief use is for the 

 destruction of the green algaa that sometimes render the water of 

 reservoirs dirty and offensive. Some of the salt contained in a gunny- 

 sack and permitted to drag to and fro over the siirface of the water 

 behind a slowly rowed boat usually accomplishes the end, the actual 

 quantity dissolving in the water being almost infinitesimal. 

 Mercuric Chlorid (HgClz). — This is probably the most generally useful as 

 well as one of the strongest germicides. 

 A study of its activity under varying conditions is instructive as exemplifying 

 the varying behavior of germicides under the varying conditions under which 

 they may be employed. 



First, it makes great diflEerence whether the mercuric chlorid is added to the 

 substratum containing the bacteria, or whether the bacteria are added to solu- 

 tions of the germicide. 



Thus, when the salt is dissolved in gelatin in a concentration of i : 1,000,000, 

 anthrax bacilli cannot grow. If it is dissolved in blood-serum, the concentration 

 must be increased to i : 10,000 to prevent their growth. 



When the anthrax spores are dropped in solutions of the salt, Kronig and Paul 

 found that they were killed in twelve to fourteen minutes by i : 65 solutions; in 

 eighty minutes by i :soo solutions, and in two hours by i : 1000 solutions. 

 When the reaction takes place in albuminous media Behring and Nochtf found 

 that much more time was required. Thus, the destruction of the spores by a 

 1 : 200 solution required eighty minutes, and a i : 1000 solution twenty-four 

 hours to completely kill all of the spores. 



LaplaceJ and Panfili§ found that the addition of 5 per cent, of tartaric or 

 hydrochloric acid facilitated the germicidal action through the prevention of 

 albuminate of mercury formation. Lubbert and Schneider and Behring have 

 used sodium chlorid and ammonium chlorid. Both of these salts diminish the 



* "Zeitschrift fiir Hygiene," 1897, xxy, i. 



tlbid.,'ix, 432. 



t "Deutsche med. Wochenschrift," 1887, 866; 1888, 121. 



§ "Ann. Ig. Roma," 1893, in, 527. 



